relnotes: add 6.5 final

rust-changelog: removed now useless early conditional for NULL_REVISION Now that the underlying `RevlogEntry` returned for `NULL_REVISION` is viable, it has become pointless to check NULL_REVISION several times, even for performance: the check will be far more frequent than the benefit of bailing earlier in the rare case where the requested revision is `NULL_REVISION`. This case is covered explicitly by the first assertion of `test_data_from_rev_null`.

rust-revlog: fix RevlogEntry.data() for NULL_REVISION Before this change, the pseudo-entry returned by `Revlog.get_entry` for `NULL_REVISION` would trigger errors in application code using it. For example, this fixes a crash spotted with changelog data while implementing RHGitaly: `Changelog.data_for_rev(-1)` was already returning the pseudo content as expected, e.g., for `hg log`, but `Changelog.entry_for_rev(-1).data()` would still crash with "corrupted revlog, hash check failed for revision -1". There is an added test for this scenario.

rust-revlog: using constant in test Always better

rust-revlog: fix incorrect results with NULL_NODE prefixes In case a short hash is a prefix of `NULL_NODE`, the correct revision number lookup is `NULL_REVISION` only if there is no match in the nodemap. Indeed, if there is a single nodemap match, then it is an ambiguity with the always matching `NULL_NODE`. Before this change, using the Mercurial development repository as a testbed (it has public changesets with node ID starting with `0005` and `0009`), this is what `rhg` did (plain `hg` provided for reference) ``` $ rust/target/debug/rhg cat -r 000 README README: no such file in rev 000000000000 $ hg cat -r 000 README abort: ambiguous revision identifier: 000 ``` Here is the expected output for `rhg` on ambiguous prefixes (again, before this change): ``` $ rust/target/debug/rhg cat -r 0001 README abort: ambiguous revision identifier: 0001 ``` The test provided by 8c29af0f6d6e in `test-rhg.t` could become flaky with this change, unless all hashes are fixed. We expect reviewers to be more sure about that than we are.

rust-revlog: split out method for `rev_from_node` without persistent nodemap This will make easier for the bug fix that is about to come.

win32mbcs: unbyteify some strings for py3 support A crash was reported on the TortoiseHg bug tracker for this[1]. [1] https://foss.heptapod.net/mercurial/tortoisehg/thg/-/issues/5905

heptapod-ci: turn off pipelines for merge request events These are always duplicated by the external (from the user) push, or internal (from Heptapod itself) push pipeline, so they're entirely redundant.

heptapod-ci: always make the default run condition explicit This has no effect on behavior, it's just to make everything obvious.

heptapod-ci: remove push exception for named branches The internal workings of Heptapod cause even fast-forward merges to look like pushes to Gitlab. The only way to run a pipeline on topic-less named branches is not through the web interface. I am probably the only person affected by this, so it's not really a problem. This was confirmed with Georges, the maintainer of Heptapod, though the only way to be *actually* sure, is to merge this and see.